Consider the following (I) The order of first ionisation enthalpy of first three elements of $3^{\text {rd }}$ period is $\mathrm{Mg}>\mathrm{Al}>\mathrm{Na}$ (II) The element with electronegativity of 3.5 is chlorine (III) The order of sizes of ions $\mathrm{Mg}^{2+}, \mathrm{Na}^{+}, \mathrm{F}^{-}$and $\mathrm{O}^{2-}$ is $\mathrm{Mg}^{2+} < \mathrm{Na}^{+} < \mathrm{F}^{-} < \mathrm{O}^{2-}$ (IV)The IUPAC name of the element with atomic number 106 is Bohrium. The correct statements are

• A

  I & II only
• B

  II & III only
• Correct answer
  C

  I & III only
• D

  II & IV only

Hence, the correct answer is option: 'C'.